Extreme Ultraviolet Photolithography Method With Developer Composition

ABSTRACT

The present disclosure provides a method for lithography patterning in accordance with some embodiments. The method includes forming a photoresist layer over a substrate, wherein the photoresist layer includes a metal-containing chemical; performing an exposing process to the photoresist layer; and performing a first developing process to the photoresist layer using a first developer, thereby forming a patterned resist layer, wherein the first developer includes a first solvent and a chemical additive to remove metal residuals generated from the metal-containing chemical.

This application claims the benefit of U.S. Provisional Application62/434,950 entitled “EXTREME ULTRAVIOLET PHOTOLITHOGRAPHY METHOD WITHDEVELOPER COMPOSITION,” filed Dec. 15, 2016, herein incorporated byreference in its entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofprocessing and manufacturing ICs. For example, as the semiconductorfabrication continues to shrink pitches below 20 nm nodes, traditionali-ArF were confronted a huge challenge. The optical restriction leads toresolution and lithography performance that cannot meet targets. Extremeultraviolet (EUV) lithography has been utilized to support criticaldimension (CD) requirements of smaller devices. EUV lithography employsscanners using radiation in the EUV region, having a wavelength of about1 nm to about 100 nm. Some EUV scanners provide 4× reduction projectionprinting onto a resist film coated on a substrate, similar to someoptical scanners, except that the EUV scanners use reflective ratherthan refractive optics. EUV lithography has imposed a complex set ofrequirements upon the resist film. The photo acid generator (PAG) in ArFresist absorbs 193 nm wave and generates photoacid, and the acid has1000 times chemical amplifier reaction (CAR) and deprotects acid labilegroup. However, the PAG is not sensitive to EUV. Due to low source powerof EUV tool and other factors, photoresist is not efficient to generateenough acid for desired resolution, leading to various patterningissues, such as line width roughness and CD uniformity. What are neededare a photoresist and a method of lithography patterning to haveimprovements in this area.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detaileddescription when read with the accompanying figures. It is emphasizedthat, in accordance with the standard practice in the industry, variousfeatures are not drawn to scale and are used for illustration purposesonly. In fact, the dimensions of the various features may be arbitrarilyincreased or reduced for clarity of discussion.

FIG. 1 illustrates a flow chart of a lithography patterning method inaccordance with some embodiments.

FIGS. 2A, 2B, 2C, 2D and 2E illustrate cross sectional views of asemiconductor structure at various fabrication stages, in accordancewith some embodiments.

FIG. 3 illustrates a resist material of FIG. 2A in accordance with someembodiments.

FIG. 4 illustrates a chemical structure of the polymer in the resistmaterial of FIG. 3 in accordance with an embodiment.

FIG. 5 illustrates a chemical structure of the ALG in the resistmaterial of FIG. 3 in accordance with an embodiment.

FIG. 6 illustrates a chemical structure of a metal-containing chemicalin the resist material of FIG. 3 in accordance with various embodiments.

FIG. 7 illustrates the metal-containing chemical of the resist materialof FIG. 3 through a lithography exposing process in accordance with anembodiment.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

The present disclosure is generally related to methods for semiconductordevice fabrication, and more particularly to compositions ofphotosensitive films in extreme ultraviolet (EUV) lithography andmethods of using the same. In lithography patterning, after a resistfilm is exposed to a radiation, such as a EUV radiation (oralternatively other radiation, such as an electron beam), it isdeveloped in a developer (a chemical solution). The developer removesportions (such as exposed portions as in a positive-tone photoresist orunexposed portions as in a negative-tone photoresist) of the resistfilm, thereby forming a resist pattern which may include line patternsand/or trench patterns. The resist pattern is then used as an etch maskin subsequent etching processes, transferring the pattern to anunderlying material layer. Alternatively, the resist pattern is thenused as an ion implantation mask in subsequent ion implantationprocesses applied to the underlying material layer, such as an epitaxialsemiconductor layer.

Generally, to produce the smallest possible circuitry, most advancedlithography systems are designed to use light of very short wavelengthsuch as for example, deep-ultraviolet light at a wavelength at or below200 nm, or extreme ultraviolet (EUV) in the region of about 13.5 nm.Such light sources are relatively weak, so the photosensitive films(e.g., a photoresist) need to be designed to utilize this light asefficiently as possible. Essentially photoresists used today formicroelectronic/nanoelectronic fabrication employ the concept ofchemical amplification to enhance the efficiency of light utilization.

A photoresist that employs the chemical amplification is generallyreferred to as a “chemically amplified resist (CAR)”. The photoresistincludes a polymer that resists to etching or ion implantation duringsemiconductor fabrication; an acid generating compound (e.g., photo acidgenerator (PAG)); and a solvent. In some examples, the polymer alsoincludes at least one acid labile group (ALG) that responds to acid. PAGabsorbs radiation energy and generates acid. The polymer and the PAG aremixed in the solvent before the photoresist is applied to a workpiece,such as a semiconductor wafer, during a lithography process. The PAG isnot sensitive to the EUV radiation. That is, advance to improvelithography efficiency (e.g., resolution/contrast, line-width-roughness,and sensitivity) encounters issues. Due to limited source power of a EUVlithography system, an existing photoresist cannot provide imagingeffect during a lithography exposure process with desired resolution andcontrast. Therefore, the disclosed photoresist further includesmetal-containing chemical to increase the sensitivity of thephotoresist. The metal-containing chemical may function as a sensitizeror through other mechanism to increase the sensitivity, which will befurther explained later. For example, the sensitizer is sensitive to EUVradiation, absorbs EUV radiation and generates electron. Thus, the PAGabsorbs electron and generates acid. However, the metal-containingchemical leaves metal residuals during subsequent processing operation,which may result in metal contamination during the subsequent processes.The disclosed photolithography process and the developer address theconcern.

FIG. 1 is a flowchart of a method 100 of patterning a substrate (e.g., asemiconductor wafer) according to various aspects of the presentdisclosure in some embodiments. The method 100 may be implemented, inwhole or in part, by a system employing advanced lithography processeswith radiation such as, extreme ultraviolet (EUV) light, or otherradiation such as deep ultraviolet (DUV) light, electron beam (e-beam)lithography, or x-ray lithography to improve pattern dimension accuracy.In the present embodiment, EUV lithography is used as the primaryexample. Additional operations can be provided before, during, and afterthe method 100, and some operations described can be replaced,eliminated, or moved around for additional embodiments of the method.

FIGS. 2A through 2E are sectional views of a semiconductor structure 200at various fabrication stages, constructed in accordance with someembodiments. The method 100 is described below in conjunction with FIG.1 and FIGS. 2A through 2E wherein the semiconductor structure 200 isfabricated by using embodiments of the method 100. The semiconductorstructure 200 may be an intermediate workpiece during the fabrication ofan integrated circuit (IC), or a portion thereof. The IC may includelogic circuits, memory structures, passive components (such asresistors, capacitors, and inductors), and active components such asdiodes, field-effect transistors (FETs), metal-oxide semiconductor fieldeffect transistors (MOSFET), complementary metal-oxide semiconductor(CMOS) transistors, bipolar transistors, high voltage transistors, highfrequency transistors, fin-like FETs (FinFETs), other three-dimensional(3D) FETs, and combinations thereof.

Referring now to FIG. 1 in conjunction with FIG. 2A, the method 100begins at block 102 with a semiconductor structure 200. Thesemiconductor structure 200 includes a substrate 202. In an embodiment,the substrate 202 is a semiconductor substrate (e.g., wafer). Infurtherance of the embodiment, the substrate 202 includes silicon in acrystalline structure. In alternative embodiments, the substrate 202includes other elementary semiconductors such as germanium, or acompound semiconductor such as silicon carbide, gallium arsenide, indiumarsenide, and indium phosphide. The substrate 202 includes one or morelayers of material or composition. The substrate 202 may include asilicon on insulator (SOI) substrate, be strained/stressed forperformance enhancement, include epitaxial regions, include isolationregions, include doped regions, include one or more semiconductordevices or portions thereof, include conductive and/or non-conductivelayers, and/or include other suitable features and layers.

In the present embodiment, the substrate 202 includes an underlayer (ormaterial layer) 204 to be processed, such as to be patterned or to beimplanted. For example, the underlayer 204 is a hard mask layer to bepatterned. In another example, the underlayer 204 is an epitaxialsemiconductor layer to be ion implanted. However, in an alternativeembodiment, the substrate 202 may not include an underlayer. In anembodiment, the underlayer 204 is a hard mask layer includingmaterial(s) such as silicon oxide, silicon nitride (SiN), siliconoxynitride, or other suitable material or composition. In an embodiment,the underlayer 204 is an anti-reflection coating (ARC) layer such as anitrogen-free anti-reflection coating (NFARC) layer includingmaterial(s) such as silicon oxide, silicon oxygen carbide, or plasmaenhanced chemical vapor deposited silicon oxide. In various embodiments,the underlayer 204 may include a high-k dielectric layer, a gate layer,a hard mask layer, an interfacial layer, a capping layer, adiffusion/barrier layer, a dielectric layer, a conductive layer, othersuitable layers, and/or combinations thereof.

In some embodiments, the structure 200 may be alternatively a photomaskused to pattern a semiconductor wafer. In furtherance of theembodiments, the substrate 202 is a photomask substrate that may includea transparent material (such as quartz), or a low thermal expansionmaterial such as silicon oxide-titanium oxide compound. The photomasksubstrate 202 may further include a material layer to be patterned. Tofurther this example, the substrate 202 may be a photomask substrate formaking a deep ultraviolet (DUV) mask, an extreme ultraviolet (EUV) mask,or other types of masks. Accordingly, the underlayer 204 is materiallayer to be patterned to define a circuit pattern. For example, theunderlayer 204 is an absorber layer, such as chromium layer for DUVphotomask or tantalum boron nitride (TaBN) for EUV photomask.

The method 100 proceeds to operation 104 with forming a photoresistlayer (or simply resist layer) 206 over the substrate 202 (FIG. 2A). Theresist layer 206 is sensitive to radiation used in a lithographyexposure process and has a resistance to etch (or implantation). In someembodiments, the resist layer 206 includes dual layer or tri-layer forlithography patterning. For example, the tri-layer resist includes abottom layer, a middle layer on the bottom layer and a photosensitivelayer on the middle layer. The bottom and middle layers are designedwith different composition for etch selectivity. In furtherance of theexample, the bottom layer is a carbon-rich polymeric material and themiddle layer is a silicon-rich material. In FIG. 2A, only photosensitivelayer is illustrated and is referred to as resist layer 206. However, itis only for illustration without limiting. It may include additionallayer, such as those in the dual layer or tri-layer resist scheme.Referring to FIG. 2A, the resist layer 206 is formed by spin-on coatingprocess in an embodiment. In some embodiments, the resist layer 206 isfurther treated with a soft baking process. The resist layer 206 issensitive to a radiation, such as I-line light, a DUV light (e.g., 248nm radiation by krypton fluoride (KrF) excimer laser or 193 nm radiationby argon fluoride (ArF) excimer laser), a EUV light (e.g., 135 nmlight), an electron beam (e-beam), and an ion beam. In the presentembodiment, the resist layer 206 is sensitive to EUV radiation.

FIG. 3 shows an embodiment of a resist material 300 of the resist layer206, constructed in accordance with some embodiments. In the presentexample, the photoresist 300 utilizes a chemical amplification (CA)resist material. For example, the CA resist material is negative toneand includes a polymer material that turns insoluble to a developer suchas a base solution after the polymer is reacted with acid. In anotherexample, the CA resist material is positive tone and includes a polymermaterial that turns soluble to a developer after the polymeric materialis reacted with acid. In yet another example, the CA resist materialincludes a polymer material that changes its polarity after the polymeris reacted with acid.

The resist material 300 is sensitive to a first radiation, such asextreme ultraviolet (EUV) light, from the radiation source of alithography system. The first radiation has a first wavelength. Theresist material 300 includes a polymer 302 to provide resistance to etch(or implantation). In various embodiments, the polymer 302 includes apoly(norbornene)-co-malaic anhydride (COMA) polymer, apolyhydroxystyrene (PHS) polymer, or an acrylate-based polymer. Forexample, the acrylate-based polymer includes a poly (methylmethacrylate) (PMMA) polymer. The PHS polymer includes a plurality ofPHS chemical structure 400 shown in FIG. 4, in which n is an integergreater than 2. The PHS chemical structure 400 includes two ends 402 and404 that are chemically linkable to other PHS chemical structures.Furthermore, PHS is also sensitive to EUV and is able to function assensitizer for EUV resist. Accordingly, a plurality of the chemicalstructures 400 are chemically bonded together (through the two ends 402and 404), thereby forming a PHS polymeric backbone. The polymer 302 alsoincludes multiple side locations that may chemically bond with otherchemicals. For example, the PHS polymer includes a plurality of hydroxyl(OH) groups 406 that may chemically bond to other chemicals.

In some examples, the resist material 300 further includes a blockinggroup 304, such as acid labile group (ALG) or dissolution inhibitor thatresponds to acid. In the present embodiment, the blocking group 304 ischemically bonded to the polymer 302, such as bonded to the OH groups406 of PHS in one example. The ALG 304 is a chemical group that isdeprotected by PAG in exposed areas of the resist layer. Thus, theexposed resist material 300 may change polarity and dissolubility. Forexample, the exposed resist material has an increased dissolubility in adeveloper (for a positive-tone resist) or decreased dissolubility in adeveloper (for a negative-tone resist). When the exposing dose of thelithography exposing process reaches a dose threshold, the exposedresist material will be dissoluble in the developer or alternatively theexposed resist material will be soluble in the developer. In oneexample, the ALG 304 includes a t-butoxycardbonyl (tBOC) 500 illustratedin FIG. 5.

The resist material 300 includes an acid generating compound 306, suchas photoacid generator (PAG). The acid generating compound (or PAG) 306absorbs radiation energy and generates acid. The resist material 300also includes a solvent 308. The polymer 302 and the acid generatingcompound 306 are mixed in the solvent 308 before the resist material isapplied to a workpiece, such as a semiconductor wafer, during alithography process. In some embodiments, the acid generating compound306 includes a phenyl ring. In a particular example, the acid generatingcompound 306 includes a sulfonium cation, such as a triphenylsulfonium(TPS) group; and an anion, such as a triflate anion. Particularly, thecation of the PAG has a chemical bond to a sulfur and an additionalchemical bond such that the sensitivity (or absorption) of the PAG tothe electron (or other type of the second radiation) is increased.

Existing PAG is not sensitive to EUV radiation. The organic elements inthe PAG or resist, such as carbon (C), nitrogen (N), and oxygen (O) areweak in EUV photon absorption. In the present disclosure, the resistmaterial 300 includes metal-containing chemical 310 to enhance EUVabsorption and resist efficiency since metals have high EUV photonabsorption. The metal-containing chemical 310 includes one or moremetallic element, such as barium (Ba), Indium (In), Cerium (Ce) or Tin(Sn). In some embodiments, the metal-containing chemical 310 is metalorganic material with metal bonded or otherwise incorporated in anorganic chemical. FIG. 6 illustrates the metal-containing chemical 310according to various examples, such as 602, 604, 606, 608, 610 or 612.The metal-containing chemical 602, 604, 606, 608 or 610 each includes Snwhile the metal-containing chemical 612 includes Antimony (Sb).Incorporating metal into the resist material may lead to metalcontamination issues in the subsequent fabrication stages. For example,when the resist layer is developed, metal residuals may be left on theworkpiece. This issue is to be addressed in the later steps of themethod 100. In some embodiments, the metal-containing chemical 310 ismixed with other chemicals (such as polymer and PAG) in the solvent 308;chemically bonded to the polymer 302; or chemically bonded to the PAG306. Alternatively, the metal-containing chemical 310 is incorporatedinto the resist material through various combinations of the abovemechanisms.

The metal-containing chemical 310 is effective to enhance EUV throughone or both of the following mechanisms. In the first mechanism, themetal-containing chemical 310 functions as a sensitizer to increase thesensitivity and efficiency of the resist material. The PAG or othercomponents of the resist material may not be sensitive to EUV but issensitive to electrons or other radiation, such UV or DUV. Thus, byincorporating the sensitizer, the resist material has an enhancedsensitivity to the first radiation. Particularly, the sensitizer issensitive to the first radiation and be able to generate a secondradiation in response to the first radiation. In the present embodiment,the first radiation is EUV radiation and the second radiation iselectron(s). The sensitizer absorbs EUV radiation and generatessecondary electron. Furthermore, PAG 306 is sensitive to the secondaryelectron, absorbs the secondary electron and generates acid.Additionally or alternatively, the sensitizer absorbs the firstradiation with a first wavelength and generates second radiation with asecond wavelength. The second wavelength is greater than the firstwavelength. In furtherance of the embodiment, the first radiation is EUVlight and the first wavelength is about 13.5 nm; and the secondwavelength ranges between 180 nm and 250 nm.

In a second mechanism illustrated in FIG. 7, the metal-containingchemical 310 each includes a metal core (such as a metal ion, labeled as“M+”) and a ligand (labeled as “L”) bonded together. During alithography exposing process (exposing process), EUV radiation isapplied to the resist material. The metal-containing chemical absorbsEUV photons and generates radicals, such as ligands and metal cores.Those radicals may directly cause crosslinking of the polymer 302 suchthat the exposed portions of the resist material remain duringdeveloping. In this case, the resist material is a negative tone resistand does not include acid-generating compound and the blocking groupsince the EUV radiation causes the crosslinking of the polymer throughthe metal-containing chemical. In furtherance of the case, the polymer302 may not be cross-linked or only partially cross-linked before thelithography exposing process.

Additionally, the resist material may further include other sensitizer,such as a fluorine-containing chemical, a phenol-containing chemical ora combination thereof. In some examples, the sensitizer includespolyhydroxystyrene, poly-fluorostyrene, or poly-chloro styrene.

Referring back to FIGS. 1 and 2B, the method 100 proceeds to operation106 by performing an exposing process to the resist layer 206 utilizingthe first radiation from a lithography system. In the presentembodiment, the first radiation is a EUV radiation (e.g., 13.5 nm). Inother embodiments, the first radiation may be an I-line (365 nm), a DUVradiation, an x-ray, an electron beam, an ion beam, and/or othersuitable radiations. The operation 106 may be performed in air, in aliquid (immersion lithography), or in a vacuum (e.g., for EUVlithography and e-beam lithography). In some embodiments, the radiationbeam is directed to the resist layer 206 to form an image of a circuitpattern defined on a photomask (such as a transmissive mask or areflective mask) in a proper exposing mode such as step-and-scan.Various resolution enhancement techniques, such as phase-shifting,off-axis illumination (OAI) and/or optical proximity correction (OPC),may be used or implemented through the photomask or the exposingprocess. For examples, the OPC features may be incorporated into thecircuit pattern on the photomask. In another example, the photomask is aphase-shift mask, such as an alternative phase-shift mask, an attenuatedphase-shift mask, or a chromeless phase-shift mask. In yet anotherexample, the exposing process is implemented in an off-axis illuminationmode. In some other embodiments, the radiation beam is directlymodulated with a predefined pattern (such as an IC layout) without usinga photomask (such as using a digital pattern generator or direct-writemode). In the present embodiment, the radiation beam is a EUV radiationand the operation 106 is performed in a EUV lithography system. Sincethe sensitivity of the resist layer 206 is enhanced and the exposingthreshold of the resist layer may be lower than 20 mJ/cm². Accordingly,the exposing process is implemented with the dose less than 20 mJ/cm²,according to the present example.

Still referring to the operation 106, after the exposing process, theoperation 106 may further include other steps, such as thermaltreatment. In the present embodiment, the operation 106 includes apost-exposure baking (PEB) process to the semiconductor structure 200,especially to the resist layer 206 coated on the substrate 202. Duringthe PEB process, according to some examples, the ALG 304 in the exposedresist material is cleaved, and the exposed portions of the resistmaterial 300 are changed chemically (such as becoming more hydrophilicor more hydrophobic). In a specific embodiment, the PEB process may beperformed in a thermal chamber at temperature ranging between about 120°C. to about 160° C.

After the operation 106, a latent pattern is formed on the resist layer206. The latent pattern of a resist layer refers to the exposed patternon the resist layer, which eventually becomes a physical resist pattern,such as by a developing process. The latent pattern of the resist layer206 includes unexposed portions 206 a and exposed portions 206 b. In thepresent case, the exposed portions 206 b of the resist layer 206 arephysically or chemically changed. In some examples, the exposed portions206 b are changed in polymerization, such as or cross-linked as innegative-tone resist or depolymerized as in positive-tone resist. Inother examples, the exposed portions 206 b are de-protected, inducingpolarity change for dual-tone imaging (developing).

Referring to FIGS. 1 and 2C, the method 100 then proceeds to operation108 by developing the exposed resist layer 206 in a developer,constructed in accordance with some embodiments. By the developingprocess, a patterned resist layer 206′ is formed. In some embodiments,the resist layer 206 is a negative-tone resist and the exposed portionsof the resist layer experience crosslinking and therefore remain afterthe developing process. In some embodiments, the resist layer 206experiences a polarity change after the operation 106, and a dual-tonedeveloping process may be implemented. For examples, the exposedportions of resist layer 206 are changed from a nonpolar state(hydrophobic state) to a polar state (hydrophilic state), then theexposed portions 206 b will be removed (positive tone imaging) by anaqueous solvent, such as tetramethyl ammonium hydroxide (TMAH), oralternatively the unexposed portions 206 a will be removed (negativetone imaging) by an organic solvent, such as butyl acetate. In someother examples, the resist layer 206 is changed from a polar state to anonpolar state, then the exposed portions 206 b will be removed(positive-tone imaging) by an organic solvent or the unexposed portions206 a will be removed (negative-tone imaging) by an aqueous solvent.

The developer is designed with chemical to form the patterned resistlayer 206′ and further effectively remove metal residuals on theworkpiece. In the present embodiment, the developer includes a solventand a chemical additive that is effective in removal of the metalresiduals and developing the resist layer. In various examples, thesolvent includes an organic solvent and may additionally include anaqueous solvent mixed with the organic solvent. Our experimental dataindicated that the effective removal of the metal residuals isdetermined by following factors of the developing process and theassociated developer: the chemical compositions and concentrations,Hansen solubility parameters, acidity, and temperature of the developer,such as a proper combination thereof. The developing process and thedeveloper are designed and tuned accordingly, which are furtherdescribed below in details.

In some embodiments, the solvent is an organic solvent designed withHansen solubility parameters (delta D, delta P, and delta H) in thefollowing ranges, 18>delta D>3, 7>delta P>1, and 7>delta H>1. Theorganic solvent may include n-Butyl acetate, Methyl n-Amyl Ketone,Hexane, Heptane, or Amyl Acetate, according to various examples.

In some other embodiments, the developer may additionally include asecond solvent mixed with the organic solvent. The second solvent isdesigned with Hansen solubility parameters (delta D, delta P, and deltaH) in the following ranges, 25>delta D>13, 25>delta P>3, and 30>deltaH>4. In this case, the organic solvent has a weight percentage greaterthan 60 w % while the second solvent has a weight percentage less than40 w %. Here a weight percentage of a solvent is defined as a weightratio as W/W0, wherein the W is the weight of the solvent while W0 isweight of the developer in a given volume. The second solvent may be anaqueous solvent or another organic solvent with a polar function group,such as —OH, —COOH, —CO—, —O—, —COOR, —CN—, —SO—, —CON—, or —NH—. Invarious examples, the second solvent is another organic solvent, such aspropylene glycol monomethyl ether (PGME), PGEE (1-Ethoxy-2-propanol),GBL (Gamma-Butyrolactone), CHN (Cyclohexanone), EL (Ethyl lactate),Methanol, Ethanol, Propanol, n-Butanol, Acetone, DMF(Dimethylformamide), Acetonitrile, Isopropyl alcohol (IPA), THF(Tetrahydrofuran), Acetic acid, or a combination thereof.

In some embodiments when the solvent includes both organic solvent andaqueous solvent mixed together, the weight percentage of the aqueoussolvent over the total weight of the developer is less than 20 w %. Theaqueous solvent includes water, ethylene glycol or a combination thereofin various examples. In this case, the aqueous solvent may be furthermixed with aqueous acid (such as hydrofluoric acid (HF) or hydrochloricacid (HCl)) or aqueous base (such as NH4OH) with weight percentage tothe total weight of the developer less than 5 w %.

The chemical additive in the developer includes organic acid, organicbase, chelate additive or a combination thereof, to enhance developingcapability. In some embodiments, chemical additive includes an organicacid tuned with the logarithmic constant pKa in a range −11<pKa<4. Infurtherance of the embodiments, the weight percentage of the organicacid in the developer ranges between 0.001 w % and 30 w %, or 0.1 w %and 20 w %. in various examples, the organic acid includes ethanedioicacid, methanoic acid, 2-hydroxypropanoic acid, 2-hydroxybutanedioicacid, Citric acid, Uric acid, Trifluoromethanesulfonic acid,Benzenesulfonic acid, ethanesulfonic acid, methanesulfonic acid, Oxalicacid dihydrate, Maleic acid, or a combination thereof.

In some embodiments, the chemical additive in the developer includes anorganic base tuned with the logarithmic constant pKa in a range40>pKa>9. In furtherance of the embodiments, the weight percentage ofthe organic base in the developer ranges between 0.001 w % and 30 w %,or 0.1 w % and 20 w %. In various examples, the organic base includesMonoethanolamine, Monoisopropanolamine, 2-Amino-2-methyl-1-propanol,1H-Benzotriazole, 1,2,4-Triazole, 1,8-Diazabicycloundec-7-ene, or acombination thereof.

In some embodiments, the chemical additive in the developer includeschelate additive having a weight percentage to the developer in a rangebetween 0.001 w % and 30 w %, or 0.1 w % and 20 w %. In variousexamples, the chelate additive includes Ethylenediaminetetraacetic acid(EDTA), Ethylenediamine-N,N′-disuccinic acid (EDDS),diethylenetriaminepentaacetic acid (DTPA), Polyaspartic acid,trans-1,2-Cyclohexanediamine-N,N,N′,N′-tetraacetic acid monohydrate,ethylenediamine, or a combination thereof.

In some embodiments, the developer further includes a surfactant with aweight percentage less than 5 w %, to increase the solubility and reducethe surface tension on the substrate.

In some embodiments, the operation 108 includes two steps, a first step108A by performing a first developing process with a first developerhaving a solvent and a chemical additive (the first developer isdescribed above in details); and a second step 108B by performing asecond developing process with a second developer, such as an existingdeveloper like n-Butyl acetate (nBA) solvent, or Methyl a-Amyl Ketone(MAK) solvent without chemical additive. In furtherance of theembodiments, the first developer in the first step 108A is heated to ahigh temperature before applied to the workpiece while the seconddeveloper in the second step 108B is not heated when or before beingapplied to the workpiece. For example, the first developer is heated toa temperature T1 in a range as, the room temperature <T1<75° C. whilethe second developer is at the room temperature without heating. Invarious examples, the first step 108A and the second step 108B may be ina different sequence (such as swapped into an opposite sequence:implement 108B first and implement 108A thereafter).

In some example illustrated in FIG. 2C, the unexposed portions 206 a areremoved in the developing process. In this example shown in FIG. 2C, thepatterned resist layer 206′ is represented by two line patterns (thistype of resist is referred to as negative tone resist). However, thefollowing discussion is equally applicable to resist patternsrepresented by trenches.

Referring to FIGS. 1 and 2D, the method 100 includes an operation 110 byperforming a fabrication process to the semiconductor structure 200using the patterned resist layer 206′ as a mask such that thefabrication process is only applied to the portions of the semiconductorstructure 200 within the openings of the patterned resist layer 206′while other portions covered by the patterned resist layer 206′ areprotected from being impacted by the fabrication process. In someembodiments, the fabrication process includes an etching process appliedto the material layer 204 using the patterned resist layer 206′ as anetch mask, thereby transferring the pattern from the patterned resistlayer 206′ to the material layer 204. In alternative embodiments, thefabrication process includes an ion implantation process applied to thesemiconductor structure 200 using the patterned resist layer as animplantation mask, thereby forming various doped features in thesemiconductor structure 200.

In the present example, the material layer 204 is a hard mask layer. Tofurther this embodiment, the pattern is first transferred from thepatterned resist layer 206′ to the hard mask layer 204, then to otherlayers of the substrate 202. For example, the hard mask layer 204 may beetched through openings of the patterned resist layer 206′ using a dry(plasma) etching, a wet etching, and/or other etching methods. Forexample, a dry etching process may implement an oxygen-containing gas, afluorine-containing gas, a chlorine-containing gas, a bromine-containinggas, an iodine-containing gas, other suitable gases and/or plasmas,and/or combinations thereof. The patterned resist layer 206′ may bepartially or completely consumed during the etching of the hard masklayer 204. In an embodiment, any remaining portion of the patternedresist layer 206′ may be stripped off, leaving a patterned hard masklayer 204′ over the substrate 202, as illustrated in FIG. 2E.

Although not shown in FIG. 1, the method 100 may include otheroperations before, during or after the operations described above. In anembodiment, the substrate 202 is a semiconductor substrate and themethod 100 proceeds to forming fin field effect transistor (FinFET)structures. In this embodiment, the method 100 includes forming aplurality of active fins in the semiconductor substrate 202. Infurtherance of the embodiment, the operation 110 further includesetching the substrate 202 through the openings of the patterned hardmask 204′ to form trenches in the substrate 202; filling the trencheswith a dielectric material; performing a chemical mechanical polishing(CMP) process to form shallow trench isolation (STI) features; andepitaxy growing or recessing the STI features to form fin-like activeregions. In another embodiment, the method 100 includes other operationsto form a plurality of gate electrodes in the semiconductor substrate202. The method 100 may further form gate spacers, doped source/drainregions, contacts for gate/source/drain features, etc. In anotherembodiment, a target pattern is to be formed as metal lines in amultilayer interconnection structure. For example, the metal lines maybe formed in an inter-layer dielectric (ILD) layer of the substrate 202,which has been etched by operation 110 to form a plurality of trenches.The method 100 proceeds to filling the trenches with a conductivematerial, such as a metal; and further proceeds to polishing theconductive material using a process such as chemical mechanicalplanarization (CMP) to expose the patterned ILD layer, thereby formingthe metal lines in the ILD layer. The above are non-limiting examples ofdevices/structures that can be made and/or improved using the method 100and the material layer 206 according to various aspects of the presentdisclosure.

The present disclosure provides a lithography process with respectivephotoresist material and developer to achieve enhanced sensitivitywithout metal contamination. The resist material includesmetal-containing chemical and the developer includes a solvent and achemical additive, such as organic acid, organic base or chelatedesigned to effectively remove the metal residuals. The developingoperation may include two steps with different developers oradditionally with different temperature. Accordingly, the sensitivity ofthe resist material is enhanced and the metal contamination iseliminated.

Thus, the present disclosure provides a method for lithographypatterning in accordance with some embodiments. The method includesforming a photoresist layer over a substrate, wherein the photoresistlayer includes a polymer, a metal-containing chemical, and an acidgenerating compound; performing an exposing process to the photoresistlayer; and performing a first developing process to the photoresistlayer using a first developer, thereby forming a patterned resist layer,wherein the first developer includes a first solvent and a chemicaladditive to remove metal residuals generated from the metal-containingchemical.

The present disclosure provides a method for lithography patterning inaccordance with some other embodiments. The method includes coating aphotoresist layer over a substrate, wherein the photoresist layerincludes a polymer, a metal-containing chemical, and an acid generatingcompound; performing an exposing process to the photoresist layer;performing a first developing process to the photoresist layer using afirst developer; and performing a second developing process to thephotoresist layer using a second developer different from the firstdeveloper, thereby forming a patterned resist layer, wherein the firstdeveloper includes a first solvent and a chemical additive toeffectively remove the metal residuals.

The present disclosure provides a method for lithography patterning inaccordance with some other embodiments. The method includes forming aphotoresist layer over a substrate, wherein the photoresist layerincludes a polymer, a metal-containing chemical, and an acid generatingcompound; performing an exposing process to the photoresist layer; andperforming a developing process to the photoresist layer. The developingprocess includes: applying a first developer of a first temperature tothe photoresist layer and applying a second developer of a secondtemperature to the photoresist layer, thereby forming a patterned resistlayer and effectively remove metal residuals. The second developer isdifferent from the first developer. The second temperature is lower thanthe first temperature. The first developer includes a first solvent anda chemical additive. The second developer includes a second solvent andis free of the chemical additive.

The foregoing outlines features of several embodiments so that those ofordinary skill in the art may better understand the aspects of thepresent disclosure. Those of ordinary skill in the art should appreciatethat they may readily use the present disclosure as a basis fordesigning or modifying other processes and structures for carrying outthe same purposes and/or achieving the same advantages of theembodiments introduced herein. Those of ordinary skill in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the present disclosure, and that they may makevarious changes, substitutions, and alterations herein without departingfrom the spirit and scope of the present disclosure.

What is claimed is:
 1. A method for lithography patterning, comprising:forming a photoresist layer over a substrate, wherein the photoresistlayer includes a metal-containing chemical; performing an exposingprocess to the photoresist layer; and performing a first developingprocess to the photoresist layer using a first developer, therebyforming a patterned resist layer, wherein the first developer includes afirst solvent and a chemical additive to remove metal residualsgenerated from the metal-containing chemical.
 2. The method of claim 1,further comprising performing a second developing process to thephotoresist layer using a second developer different from the firstdeveloper.
 3. The method of claim 2, wherein the performing of the firstdeveloping process includes heating the first developer to a firsttemperature before applied the first developer to the photoresist layer;and the performing of the second developing process includes applyingthe second developer having a second temperature lower than the firsttemperature.
 4. The method of claim 3, wherein the performing of thefirst developing process includes heating the first developer to thefirst temperature in a range greater than the room temperature and lessthan 75° C.
 5. The method of claim 2, wherein the first developingprocess is performed before the second developing process.
 6. The methodof claim 2, wherein the first developing process is performed after thesecond developing process.
 7. The method of claim 2, wherein the firstdeveloper includes the first solvent and the chemical additive, whereinthe first solvent includes an organic solvent and the chemical additiveis selected from the group consisting of an acid, a base and a chelate;and the second developer includes a second solvent and is free ofadditive.
 8. The method of claim 7, wherein the first solvent includesan organic solvent designed with Hansen solubility parameters as18>delta D>3, 7>delta P>1, and 7>delta H>1.
 9. The method of claim 8,wherein the first solvent includes an organic solvent selected from thegroup consisting of n-Butyl acetate, Methyl n-Amyl Ketone, Hexane,Heptane, Amyl Acetate or a combination thereof.
 10. The method of claim7, wherein the chemical additive in the first developer has a weightpercentage ranging between 0.001 w % and 30 w %,
 11. The method of claim10, wherein the acid in the chemical additive includes an organic acidselected from the group consisting of ethanedioic acid, methanoic acid,2-hydroxypropanoic acid, 2-hydroxybutanedioic acid, Citric acid, Uricacid, Trifluoromethanesulfonic acid, Benzenesulfonic acid,ethanesulfonic acid, methanesulfonic acid, Oxalic acid dihydrate, Maleicacid, and a combination thereof; and the organic acid is tuned with alogarithmic constant pKa in a range −11<pKa<4.
 12. The method of claim10, wherein the base in the chemical additive includes an organic baseselected from the group consisting of Monoethanolamine,Monoisopropanolamine, 2-Amino-2-methyl-1-propanol, 1H-Benzotriazole,1,2,4-Triazole, 1,8-Diazabicycloundec-7-ene, and a combination thereof;and the organic base is tuned with a logarithmic constant pKa in a range40>pKa>9.
 13. The method of claim 10, wherein the chelate in thechemical additive is selected from the group consisting of
 14. Themethod of claim 7, wherein the base in the chemical additive includes anorganic base selected from the group consisting ofEthylenediaminetetraacetic acid (EDTA), Ethylenediamine-N,N′-disuccinicacid (EDDS), diethylenetriaminepentaacetic acid (DTPA), Polyasparticacid, trans-1,2-Cyclohexanediamine-N,N,N′,N′-tetraacetic acidmonohydrate, ethylenediamine, and a combination thereof.
 14. The methodof claim 7, wherein the first developer further includes another solventmixed with the organic solvent; the another solvent in the firstdeveloper has a weight percentage less than 40 w % and the organic inthe first developer has a weight percentage greater than 60 w %; and theanother solvent is designed with Hansen solubility parameters infollowing ranges, 25>delta D>13, 25>delta P>3, and 30>delta H>4,respectively.
 15. The method of claim 14, The method of claim 14,wherein the another solvent is selected from the group consisting ofpropylene glycol monomethyl ether (PGME), PGEE (1-Ethoxy-2-propanol),GBL (Gamma-Butyrolactone), CHN (Cyclohexanone), EL (Ethyl lactate),Methanol, Ethanol, Propanol, n-Butanol, Acetone, DMF(Dimethylformamide), Acetonitrile, Isopropyl alcohol (IPA), THF(Tetrahydrofuran), Acetic acid, and a combination thereof.
 16. Themethod of claim 7, wherein the first solvent further includes an aqueoussolvent mixed with the organic solvent; the aqueous solvent in the firstdeveloper has a weight percentage less than 20 w %; and the aqueoussolvent is selected from the group consisting of water, ethylene glycoland a combination thereof.
 17. The method of claim 16, wherein theaqueous solvent is further mixed with one of aqueous acid and aqueousbase, with weight percentage to the total weight of the developer lessthan 5 w %; the aqueous acid includes at least one of hydrofluoric acid(HF) and hydrochloric acid (HCl); and the aqueous base includes NH4OH.18. A method for lithography patterning, comprising: coating aphotoresist layer over a substrate, wherein the photoresist layerincludes a polymer, a metal-containing chemical, and an acid generatingcompound; performing an exposing process to the photoresist layer;performing a first developing process to the photoresist layer using afirst developer; and performing a second developing process to thephotoresist layer using a second developer different from the firstdeveloper, thereby forming a patterned resist layer, wherein the firstdeveloper includes a first solvent and a chemical additive to remove themetal residuals.
 19. The method of claim 18, wherein the performing ofthe first developing process includes heating the first developer to afirst temperature before applied the first developer to the photoresistlayer; and the performing of the second developing process includesapplying the second developer having a second temperature lower than thefirst temperature.
 20. A method for lithography patterning, comprising:forming a photoresist layer over a substrate, wherein the photoresistlayer includes a polymer, a metal-containing chemical, and an acidgenerating compound; performing an exposing process to the photoresistlayer; and performing a developing process to the photoresist layer,wherein the developing process includes applying a first developer of afirst temperature to the photoresist layer and applying a seconddeveloper of a second temperature to the photoresist layer, therebyforming a patterned resist layer, wherein the second developer isdifferent from the first developer, wherein the second temperature islower than the first temperature; the first developer includes a firstsolvent and a chemical additive for removing metal residuals generatedfrom the metal-containing chemical, and the second developer includes asecond solvent and is free of the chemical additive.